US20120037096A1 - Combustion apparatus, method for combustion control, combustion control board, combustion control system and water heater - Google Patents
Combustion apparatus, method for combustion control, combustion control board, combustion control system and water heater Download PDFInfo
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- US20120037096A1 US20120037096A1 US12/856,860 US85686010A US2012037096A1 US 20120037096 A1 US20120037096 A1 US 20120037096A1 US 85686010 A US85686010 A US 85686010A US 2012037096 A1 US2012037096 A1 US 2012037096A1
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Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L11/00—Arrangements of valves or dampers after the fire
- F23L11/02—Arrangements of valves or dampers after the fire for reducing draught by admission of air to flues
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N1/00—Regulating fuel supply
- F23N1/02—Regulating fuel supply conjointly with air supply
- F23N1/022—Regulating fuel supply conjointly with air supply using electronic means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N1/00—Regulating fuel supply
- F23N1/04—Regulating fuel supply conjointly with air supply and with draught
- F23N1/042—Regulating fuel supply conjointly with air supply and with draught using electronic means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
- F23N5/022—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using electronic means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
- F24H1/22—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating
- F24H1/40—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating with water tube or tubes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
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- F24H15/10—Control of fluid heaters characterised by the purpose of the control
- F24H15/174—Supplying heated water with desired temperature or desired range of temperature
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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- F24H15/35—Control of the speed of fans
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H15/00—Control of fluid heaters
- F24H15/30—Control of fluid heaters characterised by control outputs; characterised by the components to be controlled
- F24H15/355—Control of heat-generating means in heaters
- F24H15/36—Control of heat-generating means in heaters of burners
- F24H15/365—Control of heat-generating means in heaters of burners of two or more burners, e.g. an array of burners
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H15/00—Control of fluid heaters
- F24H15/40—Control of fluid heaters characterised by the type of controllers
- F24H15/414—Control of fluid heaters characterised by the type of controllers using electronic processing, e.g. computer-based
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H8/00—Fluid heaters characterised by means for extracting latent heat from flue gases by means of condensation
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H9/00—Details
- F24H9/20—Arrangement or mounting of control or safety devices
- F24H9/2007—Arrangement or mounting of control or safety devices for water heaters
- F24H9/2035—Arrangement or mounting of control or safety devices for water heaters using fluid fuel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J2213/00—Chimneys or flues
- F23J2213/30—Specific materials
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2231/00—Fail safe
- F23N2231/28—Fail safe preventing flash-back or blow-back
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2241/00—Applications
- F23N2241/04—Heating water
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
Definitions
- the present invention relates to exhaust control of a combustion apparatus such as a heat pump recovering latent heat from combustion exhaust and, for example, relates to a combustion apparatus, a method for combustion control, a combustion control board, a combustion control system and a water heater that control a temperature of exhaust gas to be a predetermined temperature or below.
- a first object of the present invention is to achieve lower temperatures of combustion exhaust after heat exchange without decreasing heat efficiency of the heat exchange.
- a second object of the present invention is to select materials used for an exhaust path more freely by lowering an exhaust temperature.
- a third object of the present invention is to achieve minimizing an apparatus, that is, a compact apparatus by diluting combustion exhaust.
- a combustion apparatus of the present invention includes combustion means generating combustion exhaust by combustion of fuel; heat exchange means exchanging heat of the combustion exhaust; and exhaust dilution unit supplying dilution air after the heat exchange by the heat exchange means and diluting the combustion exhaust after the heat exchange.
- a method for combustion control of the present invention includes generating combustion exhaust by combustion of fuel; exchanging heat of the combustion exhaust; and supplying dilution air after the heat exchange of the combustion exhaust and diluting the combustion exhaust after the heat exchange.
- a combustion control board of the present invention includes a control unit taking a detected temperature of combustion exhaust, generating an output of stopping combustion if the detected temperature is equal to or over an upper temperature limit, and generating a control output permitting the combustion if the detected temperature reaches a lower temperature limit.
- a combustion control system of the present invention includes combustion means generating combustion exhaust by combustion of fuel; heat exchange means exchanging heat of the combustion exhaust; exhaust dilution unit supplying dilution air after the heat exchange by the heat exchange means and diluting the combustion exhaust after the heat exchange; and control means stopping combustion by the combustion means if the temperature of the combustion exhaust is equal to or over an upper temperature limit, and permitting the combustion if the temperature of the combustion exhaust is equal to or below a lower temperature limit.
- a water heater of the present invention includes combustion means generating combustion exhaust by combustion of fuel; heat exchange means exchanging heat of the combustion exhaust for water; and exhaust dilution unit supplying dilution air after the heat exchange by the heat exchange means and diluting the combustion exhaust after the heat exchange.
- FIG. 1 depicts an example of a water heating system according to a first embodiment
- FIG. 2 depicts an example of a water heater according to a second embodiment
- FIG. 3 is an enlarged view of a combustion chamber
- FIG. 4 is an enlarged view of an air supply tube and an exhaust dilution unit
- FIGS. 5A to 5B depict an example of structure of a backflow preventer and operation thereof
- FIGS. 6A to 6B depict an example of structure of an exhaust Hi limit and operation thereof
- FIGS. 7A to 7C depict an example of structure of the exhaust Hi limit and operation thereof
- FIG. 8 depicts an example of an electric board
- FIG. 9 is a flowchart depicting an example of processing procedure of exhaust temperature control
- FIG. 10 is a flowchart depicting an example of processing procedure of exhaust temperature control according to a third embodiment
- FIG. 11 depicts an example of a control form of a combustion fan and an exhaust dilution fan according to other embodiments
- FIG. 12 depicts an example of a control form of the combustion fan and the exhaust dilution fan according to the other embodiments.
- FIG. 13 depicts an example of a water heater according to the other embodiments.
- FIG. 1 depicts an example of a water heating system.
- a water heating system 2 is an example of a combustion apparatus, a method for combustion control, a combustion control board, a combustion control system or a water heater of the present invention.
- the water heating system 2 is installed in a room 4 , and, as depicted in FIG. 1 , provides a water heater 6 , an air supply path 8 and an exhaust path 10 .
- the water heating system 2 is an example of a combustion system combusting fuel gas G.
- the water heating system 2 is a system for exchanging heat of combustion exhaust for water to supply the heated water.
- the room 4 is an example of a room separated from a living space, and may be a space closed to the outside air such as a garage.
- a wall 12 and a ceiling 14 are separation means separating the water heating system 2 from the outside air.
- 16 is an indoor space.
- the water heater 6 is an example of a combustion apparatus combusting the fuel gas G, and has a function of exchanging heat of combustion exhaust for water to supply the heated water.
- the water heater 6 may be a latent heat recovery type water heater.
- the water heater 6 may provide a latent heat recovery type heat pump, and may provide a plurality of latent heat recovery type heat pumps for a hybrid product such as a water heater with space heating capability and a bath water heater.
- the air supply path 8 is an example of air supply means for the water heater 6 , and installed between an air supply part (for example, a sidewall vent) 18 placed in the wall 12 and the water heater 6 .
- a stay rod 20 is provided for the air supply path 8 at its middle. In the embodiment, the stay rod 20 fixes the air supply path 8 to the ceiling 14 .
- the exhaust path 10 is an example of exhaust means from the water heater 6 , and is installed between an exhaust part (terminator) 22 placed in the wall 12 and the water heater 6 .
- a stay rod 24 is provided for the exhaust path 10 at its middle. In the embodiment, the stay rod 24 fixes the exhaust path 10 to the ceiling 14 .
- the air supply part 18 and the exhaust part 22 are placed separately from each other to prevent combustion exhaust from being supplied into the air supply part 18 .
- FIG. 2 depicts an example of a water heater and FIG. 3 depicts an enlarged combustion chamber of the water heater.
- the water heater 6 is an example of a combustion apparatus of the present invention.
- the water heater 6 exchanges heat of combustion exhaust for water W to supply hot water HW.
- a housing 26 is provided for the water heater 6 .
- a combustion chamber 28 is placed in the housing 26 .
- the housing 26 is a sealed space.
- An air supply tube 30 is formed on the housing 26 for supplying air into the sealed space.
- the above described air supply path 8 is connected to the air supply tube 30 , and air supply A is executed via the air supply tube 30 and the air supply path 8 .
- the combustion chamber 28 is a combustion space.
- An exhaust dilution unit 32 is provided for the combustion chamber 28 on its top.
- An exhaust tube 34 is formed on the exhaust dilution unit 32 .
- the exhaust tube 34 is separated from the sealed space of the housing 26 .
- the above described exhaust path 10 is connected to the exhaust tube 34 , and exhaust E is vented via the exhaust tube 34 and the combustion exhaust path 10 .
- a burner 36 , a primary heat exchanger 38 and a secondary heat exchanger 40 are placed in the combustion chamber 28 .
- the burner 36 is an example of combustion means combusting fuel gas G, and provides a first burner unit 362 , a second burner unit 364 and a third burner unit 366 .
- a guide 367 surrounding these burner units 362 , 364 and 366 is placed.
- a partition 369 between the burner unit 362 and the burner unit 364 , and a partition 370 between the burner unit 364 and the burner unit 366 respectively partition a space for the burner units into an individual space.
- a combustion fan 42 is placed below the burner units 362 , 364 and 366 .
- Combustion air A 1 is supplied to the combustion fan 42 from the air A supplied into the housing 26 .
- a main valve 46 , a proportional valve 48 and changeover valves 50 , 52 and 54 are placed in a gas supply pipe 44 that supplies the fuel gas G to the burner 36 as means supplying and adjusting the supply of the fuel gas G, or closing the supply thereof.
- the main valve 46 is placed most upstream of the gas supply pipe 44 , and is a changeover valve for supplying or closing the supply of the fuel gas G.
- the proportional valve 48 adjusts the supply of the fuel gas G of flowing in the gas supply pipe 44 .
- the changeover valves 50 , 52 and 54 correspond to the burner units 362 , 364 and 366 , respectively, and are switching means for selecting a burner unit for combustion from the burner units 362 , 364 and 366 .
- a gas supply source is connected to a gas supply inlet 55 of the gas supply pipe 44 , and the fuel gas G is supplied therefrom.
- a spark plug 56 , a flame detection rod 58 and a self-check flame rod 60 are provided for a combustion outlet of the burner 36 .
- An igniter 62 placed outside the combustion chamber 28 is connected to the spark plug 56 .
- the primary heat exchanger 38 is an example of a first heat exchange means, is placed upstream of combustion exhaust E generated by the combustion of the burner 36 , and mainly exchanges sensible heat from the combustion exhaust E for the water W.
- the secondary heat exchanger 40 is an example of a second heat exchange means, is placed more downstream than the primary heat exchanger 38 , and mainly exchanges latent heat from the combustion exhaust E after the primary heat exchange for the water W.
- a drain vessel 64 is placed below the secondary heat exchanger 40 .
- the drain vessel 64 receives drain (waste field) D generated in the secondary heat exchanger 40 by secondary heat exchange.
- a drainpipe 66 is connected to the drain vessel 64 .
- the drain D received by the drain vessel 64 is introduced through the drainpipe 66 to a drain outlet 68 of the housing 26 to be discharged.
- a water supply path 70 is connected to the secondary heat exchanger 40 , and the water W is supplied to the secondary heat exchanger 40 prior to the primary heat exchanger 38 .
- a tap water path is connected to a water supply inlet 71 of the water supply path 70 , and the water W such as tap water is supplied therefrom.
- the inlet of the primary heat exchanger 38 is linked to the outlet of the secondary heat exchanger 40 by a joint path 72 , and the hot water HW obtained by the secondary heat exchange flows into the primary heat exchanger 38 via the joint path 72 .
- a hot water path 74 is connected to the outlet of the primary heat exchanger 38 , and the hot water HW heated by the primary heat exchange flows into the hot water path 74 .
- a bypath circuit 76 across the primary heat exchanger 38 is provided between the water supply path 70 and the hot water path 74 .
- the bypath circuit 76 is means for running the water W into the hot water HW.
- a bypath valve 78 is placed at the inlet of the bypath circuit 76 (water supply path 70 side).
- the flow rate of the water W supplied to the hot water HW via the bypath circuit 76 is determined according to the opening of the bypath valve 78 .
- a flow rate sensor 79 is placed in the water supply path 70 for detecting the flow rate.
- a water control valve 82 is placed between the hot water path 74 and a hot water supply path 80 . The flow rate of the outgoing hot water HW is controlled according to the opening of the water control valve 82 and thus, the supply of the water W is controlled.
- a temperature sensor 84 is placed at the water supply path 70 , and detects the temperature of supplied water.
- a heat exchange Hi limit 86 and a hot water temperature sensor 88 are placed at the outlet of the primary heat exchanger 38 , and the temperature of the hot water HW is detected.
- a mixture temperature sensor 90 is placed at the hot water supply path 80 , and detects the temperature of the mixture of the hot water HW and the water W.
- the heat exchange Hi limit 86 is the same structure as an exhaust Hi limit 106 ( FIG. 6 ) described below.
- a hot water supply pipe 93 supplying hot water to a demanded place such as a house's interior is connected to a hot water outlet 91 of the hot water supply path 80 , and a hot water faucet 95 is provided thereto.
- the hot water faucet 95 may be a shower valve.
- the exhaust dilution unit 32 is formed on the top of the combustion chamber 28 , is an exhaust path bent by a first path wall 92 and a second path wall 94 , and provides an exhaust dilution duct 96 on the top of the combustion chamber 28 .
- the exhaust dilution duct 96 communicates with a path 98 surrounded by the path walls 92 and 94 .
- An exhaust dilution fan 100 is placed at the exhaust dilution duct 96 , and air supply A 2 from the housing 26 is taken into the path 98 through the exhaust dilution duct 96 by the exhaust dilution fan 100 .
- the air supply A 2 is mixed with the combustion exhaust E, and the combustion exhaust E is diluted by the air supply A 2 .
- a backflow preventer 102 and a partition 104 are placed in the exhaust dilution duct 96 as air flow guides.
- the backflow preventer 102 is an example of backflow preventing means that prevents the combustion exhaust E from flowing back to the exhaust dilution fan 100 .
- the partition 104 prevents the air supply A 2 from intruding into the secondary heat exchanger 40 .
- the exhaust Hi limit 106 ( FIG. 6 ) and an exhaust temperature sensor 108 are placed at the exhaust dilution unit 32 .
- the exhaust Hi limit 106 is an example of a temperature detection switch.
- the exhaust Hi limit 106 monitors the temperature of the combustion exhaust E and if 69 (° C.) is detected as a predetermined temperature, the exhaust Hi limit 106 becomes non-conducts.
- the exhaust temperature sensor 108 is an example of a temperature sensor detecting an exhaust temperature.
- An electric board 110 is placed in the housing 26 .
- the electric board 110 is electric control means for the water heater 6 and is an example of a combustion control board.
- An electrical supply line 112 is connected to the electric board 110 , and an AC source is inputted via a surge box 114 , a transformer 116 and GFI 118 .
- the surge box 114 is means for absorbing a surge from an AC source and the transformer 116 transforms an AC source to a predetermined voltage.
- the water heater 6 As to the water heater 6 , described will be (a) a start of water heating and combustion operation, (b) heat exchange operation, (c) exhaust dilution operation of the exhaust dilution unit 32 , (d) air supply and exhaust operation, (e) hot water outgoing temperature control, (f) combustion control of the burner 36 and (g) drain discharge operation.
- the water heater 6 when the hot water supply faucet 95 of a shower etc. connected to the hot water supply path 80 is opened, the water W flows into the water supply path 70 .
- the temperature of supplied water is detected by the temperature sensor 84 and the flow rate of supplied water is detected by the water rate sensor 79 .
- the detected information is inputted to the electric board 110 .
- the main valve 46 is opened, the changeover valve 50 , 52 or 54 is opened, and the burner 36 is ignited by the operation of the igniter 62 and the spark plug 56 .
- the combustion fan 42 starts working, and combustion air (the air supply A 1 ) is supplied to the burner 36 from the air supply A supplied from the air supply tube 36 to the housing 26 .
- the fuel gas G mixed with the air supply A 1 is combusted in the burner 36 . This combustion generates the combustion exhaust E of high temperatures in the combustion chamber 28 .
- the combustion exhaust E flows into the primary heat exchanger 38 at a downstream side assuming that the burner 36 in the combustion chamber 28 is upstream.
- sensible heat is mainly absorbed from the combustion exhaust E to be exchanged for the water W (primary heat exchange).
- the combustion exhaust E after the primary heat exchange flows into the secondary heat exchanger 40 .
- latent heat is mainly absorbed from the combustion exhaust E after the primary heat exchange to be exchanged for the water W (secondary heat exchange).
- the combustion exhaust E after the primary heat exchange and the secondary heat exchange is cooled with its sensible heat and latent heat being absorbed, diluted by being mixed with the air supply A 2 by the exhaust dilution unit 32 to be further cooled, and then vented to the outside through the exhaust tube 34 and the exhaust path 10 .
- the exhaust dilution fan 100 starts rotating at the same time when the burner 36 starts combusting, and the backflow preventer 102 at the exhaust dilution duct 96 is opened. If the exhaust dilution fan 100 rotates, the air A 2 is sent from the housing 26 to the exhaust dilution duct 96 , and the air A 2 is supplied from the exhaust dilution duct 96 to the exhaust dilution unit 32 .
- the air A 2 joins the combustion exhaust E after the secondary heat exchange, the combustion exhaust E is diluted by the air supply A 2 , and thus the combustion exhaust E after the secondary heat exchange is further cooled.
- the temperature of the combustion exhaust E in the exhaust dilution unit 32 is monitored by the exhaust Hi limit 106 and the exhaust temperature sensor 108 .
- a setting temperature of the exhaust Hi limit 106 for example, 69 (° C.)
- the exhaust Hi limit 106 becomes non-conducts. Thereby, the temperature of the combustion exhaust E is lowered by the control of the combustion of the burner 36 etc.
- Air is supplied from the outside to the water heater 6 via the air supply pipe 8 , and the combustion exhaust E is vented to the outside via the exhaust path 10 .
- the rotation of the exhaust dilution fan 100 is associated with that of the combustion fan 42 . If the rotation speed of the combustion fan 42 is reduced, the rotation speed of the exhaust dilution fan 100 is reduced. On the contrary, if the rotation speed of the combustion fan 42 is increased, the rotation speed of the exhaust dilution fan 100 is also increased. As the above, the rotation of the exhaust dilution fan 100 and combustion fan 42 may be associated and may be independent.
- the water W flows into the secondary heat exchanger 40 .
- the water W flows into the primary heat exchanger 38 , and then heat exchange is executed with sensible heat of the combustion exhaust E at the upstream side (primary heat exchange).
- the temperature of the hot water HW in the outlet of the primary heat exchanger 38 is detected by the hot water temperature sensor 88 at the outlet of the primary heat exchanger 38 .
- the bypath valve 78 is opened, the water W flows into the bypath circuit 76 to be mixed with the hot water HW, and the temperature of the hot water HW is controlled to be the target temperature.
- the temperature of the hot water HW is detected by the mixture temperature sensor 90 at the hot water supply path 80 .
- the hot water HW is supplied to the above described shower etc.
- the temperatures detected by the mixture temperature sensor 90 are inputted to the electric board 110 continuously, and is used for the opening control of the water control valve 82 as control information.
- the flow rate is controlled to be a flow rate necessary to reach the target temperature by the opening of the water control valve 82 .
- the hot water HW is supplied from the hot water supply path 80 .
- the burner units 362 , 364 and 366 in the burner 36 are switched by the opening and closing of the changeover valves 50 , 52 and 54 on the condition that the main valve 46 at the gas supply pipe 44 is open, and the supply of the fuel gas G is adjusted according to the opening of the proportional valve 48 to control the combustion of the fuel gas G.
- the drain D includes impurities in the combustion exhaust E.
- the drain D is pooled in the drain vessel 64 placed below the secondary heat exchanger 40 , introduced from the drain 66 to the drain outlet 68 , and discharged to the outside of the water heater 6 .
- FIG. 4 depicts the mixture of combustion exhaust and dilution air in the exhaust dilution part
- FIGS. 5A to 5B depict a function of the backflow preventer
- FIGS. 6A to 6B depict the structure of the exhaust Hi limit and operation thereof.
- FIGS. 4 to 6B the same components as those in FIGS. 2 to 3 are denoted by the same reference numerals.
- the exhaust dilution unit 32 is means for mixing the air A 2 with the combustion exhaust E after heat exchange, diluting the combustion exhaust E by the air A 2 , and lowering the temperature of the combustion exhaust E further than that after the heat exchange.
- the combustion exhaust E whose sensible heat is absorbed by the heat exchange in the primary heat exchanger 38 and whose latent heat is absorbed by the heat exchange in the secondary heat exchanger 40 , lowers its temperature to 80 (° C.) (176 (° F.)) or so.
- the exhaust pipe 10 can stand the heat of the temperature if a metal tube is used therefore, if a resin tube is used for the exhaust pipe 10 , it is needed to lower the temperature of the combustion exhaust E below heat proof temperature of the resin.
- the temperature of the combustion exhaust E passing through the exhaust dilution unit 32 is lowered below 69 (° C.) (156 (° F.)).
- CSA Canadian Standard Association
- the exhaust dilution unit 32 is placed in order to apply to such standard.
- the exhaust dilution unit 32 is a function unit taking the air A 2 of the room temperature thereinto by rotating the exhaust dilution fan 100 , diluting the combustion exhaust E by mixing the air A 2 with the combustion exhaust E, and cooling combustion exhaust E to equate or lower the temperature of the combustion exhaust E flowing in the exhaust tube 34 to or below the standard temperature.
- the exhaust dilution unit 32 is placed downstream of the combustion chamber 28 .
- the exhaust dilution duct 96 is provided for the exhaust dilution unit 32 .
- the exhaust dilution fan 100 is provided for the exhaust dilution duct 96 to take the air A 2 .
- the air A 2 is efficiently mixed with the combustion exhaust E after the secondary heat exchange by providing the backflow preventer 102 and the partition 104 .
- the exhaust dilution fan 100 rotates, the air A 2 is taken from the inside space of the housing 26 into the exhaust dilution duct 96 , the backflow preventer 102 is opened, and the partition 104 guides an air flow.
- the combustion exhaust E passing through the secondary heat exchanger 40 is taken into the air supply A 2 guided by the partition 104 to be joined, and the air A 2 is mixed with the combustion exhaust E.
- the partition 104 guides the air A 2 to introduce the air A 2 to the path wall 92 and thus, the air A 2 joins the combustion exhaust E reaching the path 92 without preventing the combustion exhaust E at the secondary heat exchanger 40 from rising.
- Such an air flow guiding function of the partition 104 efficiently mixes the combustion exhaust E and the air A 2 , and prevents the air A 2 from flowing into the secondary heat exchanger 40 .
- the secondary heat exchanger 40 does not touch the air A 2 , and the decrease of the efficiency of the heat exchange of the secondary heat exchanger 40 can be prevented.
- the backflow preventer 102 placed at the inlet of the exhaust dilution duct 96 prevents the combustion exhaust E from flowing back to the exhaust dilution fan 100 to prevent the combustion exhaust E from being mixed with the air A 1 . If there is no backflow preventer 102 and a contrary wind occurs, the outlet of the exhaust dilution fan 100 is shut to cause the combustion exhaust E to flow back to the air supply outlet of the exhaust dilution fan 100 . If the combustion exhaust E flows into the space of the housing 26 , the combustion exhaust E is absorbed into the combustion fan 42 , and combustion failure of the burner 36 is generated by the exhaust obstruction. This is exhaust recycling by a backflow of the combustion exhaust E.
- the occurrence of the above described exhaust recycling is prevented by closing the backflow preventer 102 .
- the backflow preventer 102 is closed, the temperature of the combustion exhaust E in the exhaust dilution unit 32 increases since the air A 2 is not supplied to the exhaust dilution duct 96 .
- This increase of the temperature is detected by the exhaust temperature sensor 108 .
- the temperature detected by the exhaust temperature sensor 108 is informed to the electric board 110 rapidly.
- combustion control that the combustion of the burner 36 is immediately decreased is performed.
- the occurrence of the combustion failure due to the backflow of the combustion exhaust E can be prevented and the temperature rising in the exhaust dilution unit 32 can be surely prevented by adjusting the combustion.
- the backflow preventer 102 is an example of backflow preventing means. As depicted in FIG. 5A , the backflow preventer 102 is rotatably supported at the outlet of the exhaust dilution fan 100 by a hinge 101 , and opens and closes the exhaust dilution duct 96 by the force of wind (wind pressure). If the exhaust dilution fan 100 is operated, the air supply A 2 is generated. The backflow preventer 102 is opened in response to the air supply A 2 and the air supply A 2 flows into the exhaust dilution duct 96 . If the exhaust dilution fan 100 stops, the backflow preventer 102 restores a closed position by its own weight as depicted in dashed lines.
- the exhaust Hi limit 106 is, as depicted in FIG. 6A , a temperature detection switch including a temperature detection part 107 and opening and closing contact 109 .
- the temperature detection part 107 may be made of a bimetal.
- the opening and closing contact 109 is a contact opened and closed by a bimetal.
- FIG. 7A depicts the principle of the temperature detection part of the exhaust Hi limit
- FIGS. 7B and 7C depict switching structure of the exhaust Hi limit and the operation thereof.
- a bimetal 136 is used for the temperature detection part 107 as depicted in FIG. 7A that is made by uniting a high expansion coefficient metal 132 presenting high expansion by heating and a low expansion coefficient metal 134 of lower expansion than the high expansion coefficient metal 132 .
- the bimetal 136 is supported so as to be able to change the position of its ends. The position thereof is changed from that depicted by solid lines before heating to that depicted by broken lines after heating.
- the exhaust Hi limit 106 is a sensing temperature switch providing the bimetal 136 at the temperature detection part 107 .
- a pin 138 touching its end to the bimetal 136 is movably held by a retainer 140 in the exhaust Hi limit 106 as depicted in FIG. 7B .
- a spring 144 is inserted between another end of the pin 138 and a case 142 . Restoring force of the spring 144 acts.
- a fixing contact 146 is attached to a fixing piece 145 fixed to the case 142 .
- a movable contact 148 is attached to the spring 144 .
- the movable contact 148 touches the fixing contact 146 to maintain a closed state (a state of the opening and closing contact 109 depicted by solid lines in FIG. 6A ).
- the movable contact 148 separates from the fixing contact 146 since the pin 138 receiving the change of the bimetal 136 drops down to compress the spring 144 (a state of the opening and closing contact 109 depicted by broken lines in FIG. 6A ).
- a temperature is detected and opening and closing of the fixing contact 146 and the movable contact 148 is realized.
- a cap 152 is attached to the top of the case 142 intervening a spacer 150 between the cap 152 and the retainer 140 .
- the case 142 is provided with an attachment 154 .
- a terminal 156 is placed at the bottom of the case 142 .
- the terminal 156 is connected to the movable contact 148 in the spring 144 , and a different terminal is provided for the fixing contact 146 in the fixing piece 145 . Therefore, the case 142 is fixed to an outer wall of the dilution exhaust unit 32 by the attachment 154 , and an output by the opening and closing of the fixing contact 146 and the movable contact 148 based on temperature detection can be obtained.
- FIG. 8 depicts an example of the structure of an electric board.
- the same components as those in FIGS. 2 to 4 are denoted by the same reference numerals.
- the electronic board 110 is an example of a combustion control board or a combustion control system of the present invention, and provides a control unit 120 .
- the control unit 120 is an example of control means, maybe composed of a microcomputer, and, for example, provides a CPU (Central Processing Unit) 122 , a ROM (Read-Only Memory) 124 , a RAM (Random-Access Memory) 126 , an input/output unit (I/O) 128 and a timer 130 .
- a CPU Central Processing Unit
- ROM Read-Only Memory
- RAM Random-Access Memory
- I/O input/output unit
- the CPU 122 is an example of calculation means executing various calculation, determining means for detection information and control means for generating a control output etc.
- the CPU 122 executes a control program in the ROM 124 and generates a control output based on combustion control on the basis of a flame determination result, detected temperatures, detected flow rates, etc.
- the ROM 124 is an example of storage means storing a control program etc.
- the RAM 126 composes an execution area of a program.
- the I/O 128 is an example of an input unit taking detection information etc. and an output unit outputting a control output to various function units.
- the timer 130 is an example of time keeping means and measures combustion time etc.
- Start and stop information on driving is inputted from a driving switch 121 to the control unit 120 of the electric board 110 .
- flow rate information is inputted from the flow rate sensor 79 to the control unit 120 and temperature information etc. are inputted from the temperature sensor 84 , the hot water temperature sensor 88 , the mixture temperature sensor 90 and the exhaust Hi limit 106 to the control unit 120 .
- Rotating speed information etc. is inputted from the combustion fan 42 and the exhaust dilution fan 100 of the air supply unit is also inputted to the control unit 120 .
- Information whether there is FR current or not and information on current measured value as flame detection information from a flame rod are also inputted to the electric board 110 .
- Control information based on the input information is outputted to the combustion fan 42 , the exhaust dilution fan 100 , the main valve 46 , the proportional valve 48 , the changeover valves 50 , 52 and 54 , the water control valve 82 , the igniter 62 and other function units 63 .
- the other function units 63 may include informing means 65 such as a speaker, a buzzer and a display.
- This temperature control of the combustion exhaust E is realized by controlling the volume of combustion or flow rate of outgoing hot water according to the temperature detected by the exhaust temperature sensor 108 while the combustion is maintained. Since the amount of the combustion (the fuel supply rate) and the flow rate of outgoing hot water are linked, the fuel supply rate may be adjusted or the flow rate of outgoing hot water may be adjusted.
- the maximum combustion capacity (unit used in Japan: “gou”) is gradually reduced.
- the temperature of the combustion exhaust E is lowered to the lower temperature limit L, the maximum combustion capacity (“gou”) is gradually increased.
- the temperature of the combustion exhaust E is controlled to be within predetermined temperatures. In this case, the temperature of outgoing hot water is kept in setting temperatures.
- the range of “gou” (1 to 5 (gou)) maybe changed according to the temperature of the combustion exhaust E as another way.
- the flow rate of outgoing hot water is reduced by narrowing the opening of the water control valve 82 .
- the flow rate of outgoing hot water is increased by the degree of the opening of the water control valve 82 .
- the temperature of the combustion exhaust E is controlled to be within predetermined temperatures. In this case, the temperature of outgoing hot water is also kept in setting temperatures.
- the above described “gou” (Japanese) represents the water heating capacity of the water heater 6 .
- 1 (gou) is the capacity that the temperature of 1 (L) of water W is raised by 25 (° C.) a minute.
- the capacity an hour is
- the formula (1) represents that the combustion and the flow rate are increased and decreased in proportion to “gou”.
- “gou” is determined by the deference between a supplied water temperature and an outgoing hot water temperature, and the flow rate. Assuming that a supplied water temperature and outgoing hot water temperature are constant, the temperature of the combustion exhaust E depends on “gou”. Therefore, it is found that in order to lower the temperature of the combustion exhaust E, “gou” may be decreased.
- the above described water heater 6 controls the combustion of the burner 36 so that an outgoing hot water temperature becomes setting temperatures. If the flow rate changes, the combustion of the burner 36 is controlled according to the change to control the hot water supply temperature within setting temperatures. If the maximum regulated flow rate is gradually reduced by the opening of the water control valve 82 , “gou” decreases along therewith. That is, the decrease of “gou” is narrowing the opening of the proportional valve 48 , and thereby, the maximum combustion capacity is regulated. In the other words, if the opening of the proportional valve 48 is gradually narrowed, the opening of the water control valve 82 is gradually narrowed along therewith, the flow rate of supplied hot water is reduced, and the temperature of outgoing hot water is kept constant.
- an outgoing hot water temperature may be changed by adjusting setting temperatures. If an outgoing hot water temperature is changed to keep the flow rate constant, the above described “gou” results in changing.
- FIG. 9 depicts an example of processing procedure of exhaust temperature control.
- This processing procedure is an example of a method for the combustion control or a combustion control program of the present invention.
- the processing procedure includes the above described temperature control of the combustion exhaust E.
- the upper temperature limit 69 (° C.) and the lower temperature limit 55 (° C.) are set in order to realize the control according to the temperature detected by the exhaust temperature sensor 108 .
- a second temperature 66 (° C.) is set between these upper temperature limit (set in 69 (° C.) as a first temperature in the procedure) and the lower temperature limit (set in 55 (° C.) as a fifth temperature in the procedure.
- a second temperature 66 (° C.)
- a third temperature 63 (° C.) and a fourth temperature 60 (° C.) are set.
- the processing procedure starts from the power turned ON.
- Clearing subtract values for the regulated flow rate is executed as an initial reset (step S 101 ).
- a reset of data representing “gou” regulation before the driving switch 121 turned ON (the maximum regulated flow rate and the maximum combustion capacity regulation value) is executed, and the maximum “gou” of an initial setting is set again.
- step S 102 After the power ON, the operation of the driving switch 121 is monitored (step S 102 ). If the driving switch 121 is not turned ON (NO of step S 102 ), the procedure returns to step S 101 to be standby.
- step S 102 If the driving switch 121 is turned ON (YES of step S 102 ), the flow rate of supplied water is monitored (step S 103 ). If the flow rate detected by the flow rate sensor 79 is below a predetermined flow rate (NO of step S 103 ), the procedure becomes standby.
- step S 103 If the flow rate detected by the flow rate sensor 79 is equal to or over the predetermined flow rate (ON) (YES of step S 103 ), the combustion fan 42 and the exhaust dilution fan 100 are operated since a demand for hot water is generated by the opening of the hot water supply faucet 95 .
- the combustion of the fuel gas G is started by the burner 36 and the combustion is maintained (step S 104 ).
- the temperature of the combustion exhaust E is detected by the exhaust temperature sensor 108 and the switching operation of the exhaust Hi limit (HHL) 106 is monitored (step S 105 ).
- the temperature detected by the exhaust temperature sensor 108 and closing information or opening information of the exhaust Hi limit 106 are taken into the control unit 120 .
- step S 105 When the exhaust Hi limit 106 is opened (YES of step S 105 ), the combustion of the burner 36 is stopped and “gou” is decreased, for example, by 5 (gou) to reduce the regulated flow rate (step S 106 ).
- step S 107 The opening or closing of the exhaust Hi limit 106 is continuously monitored, (step S 107 ). If the exhaust Hi limit 106 is closed (NO of step S 107 ), the procedure returns to step S 104 .
- the flow rate OFF is the flow rate possible to be regarded as OFF by reducing the flow rate of supplied water.
- the driving OFF is a state where the driving switch 121 is switched OFF.
- step S 108 If the flow rate or driving is OFF (YES of step S 108 ), the procedure returns to step S 101 . If the flow rate or driving is not OFF (NO of step S 108 ), the procedure returns to step S 107 .
- steps S 105 to S 108 if the exhaust dilution unit 32 is cooled down and the exhaust Hi limit 106 is closed after the combustion is stopped, the combustion is restarted. However, though the combustion is restarted, the combustion is stopped again if the temperature of the combustion exhaust E is higher. Thus, subtraction of the regulated flow rate is executed that the combustion is reduced by 5 (gou) from “gou” when the combustion is stopped to make the exhaust temperature equate to or lower below the predetermined temperature. In this case, driving can be restarted by once closing and then reopening the hot water supply faucet 95 , or by once turning the driving switch 121 OFF and then ON again. At that time, the subtract value of the regulated flow rate is cleared. If such processes are repeated, the control unit 120 determines that there is some anomaly, and an alarm may be given from the informing means 65 .
- step S 105 If the exhaust Hi limit 106 is closed (NO of step S 105 ), the temperature detected by the exhaust temperature sensor 108 (HTH) is monitored and control according to the detected temperature is executed (steps S 109 to S 124 ).
- stopping the combustion stopping the combustion, reducing “gou” by 5 (gou) and reducing the regulated flow rate are executed (step S 111 ), and it is determined whether the temperature of the combustion exhaust E is
- a predetermined time for example, 5 (sec) have passed since the detection of the second temperature
- detection time and the subtract value of the regulated flow rate vary according to the detected temperature of the combustion exhaust E. For example, if the detected temperature of the combustion exhaust E is equal to or over 69 (° C.), whether detection time, for example, 1 (sec) has passed or not is determined. If at least 1 (sec) or over has passed in a state that the temperature is equal to or over 69 (° C.), the combustion is stopped (step S 111 ). When the combustion is stopped, subtraction of the regulated flow rate is executed and the exhaust temperature is controlled. After that, if the exhaust temperature sensor 108 detects the temperature 55 (° C.) or below, the combustion is restarted.
- step S 101 the subtract value of the regulated flow rate is cleared (step S 101 ) by once closing, and then reopening the hot water supply faucet 95 to enable the combustion to be restarted.
- step S 101 the subtract value of the regulated flow rate is cleared (step S 101 ) to enable the combustion to be restarted.
- step S 116 it is determined whether the detected temperature is equal to or over the third temperature, for example, 63 (° C.), or not (step S 116 ). It is determined whether or not a predetermined time, for example, 20 (sec) have passed since the detection of the third temperature (step S 117 ). If (sec) have passed (YES of step S 117 ), reducing “gou” by 3 (gou) and reducing the regulated flow rate are executed (step S 118 ), and the procedure returns to step S 102 .
- a predetermined time for example, 20 (sec) have passed since the detection of the third temperature
- steps S 116 to S 118 if the exhaust temperature is below 66 (° C.), whether to be equal to or over a predetermined temperature, for example, 63 (° C.), or not is determined. If the exhaust temperature is equal to or over 63 (° C.), it is determined whether detection time, for example, (sec) have passed or not. If the exhaust temperature 63 (° C.) or over have been maintained for 20 (sec), subtraction of the regulated flow rate (3 “gou”) is executed and the exhaust temperature is limited.
- a predetermined temperature for example, 63 (° C.)
- Differentiating and setting monitoring time longer than step S 115 are because accurate temperature information is needed to be taken in since there requires a predetermined time till the flow rate regulation due to continuous temperature detection and since the result of the regulation is not reflected in the exhaust temperature unless a predetermined time has passed from the flow rate regulation.
- a predetermined time for example, 90 (sec) have passed since the detection of the fourth temperature (step S 120 ). If 90 (sec) have passed (YES of step S 120 ), reducing “gou” by 1 (gou) and reducing the regulated flow rate are executed (step S 121 ), and the procedure returns to step S 102 .
- steps S 119 to S 121 if the exhaust temperature is below 63 (° C.), whether to be equal to or over a predetermined temperature, for example, 60 (° C.), or not is determined. If the exhaust temperature is equal to or over 60 (° C.), it is determined whether detection time, for example, 90 (sec) have passed or not. If the exhaust temperature 60 (° C.) or over has been maintained for 90 (sec), subtraction of the regulated flow rate (1 “gou”) is executed and the exhaust temperature is limited.
- step S 117 Setting monitoring time longer than step S 117 as well is because accurate temperature information is needed to be taken in since there requires a predetermined time till the flow rate regulation due to continuous temperature detection and since the result of the regulation is reflected in the exhaust temperature unless a predetermined time has passed from the flow rate regulation.
- step S 122 to S 124 if the exhaust temperature is below 60 (° C.), whether to be equal to or below a predetermined temperature, for example, 55 (° C.), or not is determined. If the exhaust temperature is equal to or below 55 (° C.), it is determined whether detection time, for example, 100 (sec) have passed or not. If the exhaust temperature 55 (° C.) or below has been maintained for 100 (sec), the regulated flow rate is increased by 1 “gou” to release the regulation of the exhaust temperature. Although the regulated flow rate is increased, the procedure returns to step S 102 again to confirm the change of the temperature of the combustion exhaust E after the control to detect the temperature. Increasing the regulated flow rate increases the hot water outgoing capacity again. For example, when the regulated flow rate increases more than need or when outgoing hot water is reduced or a setting temperature is lowered during use, the hot water outgoing capacity can be increased.
- the opening of the water control valve 82 is narrowed and the regulated flow rate is reduced by 5 (gou) if the temperature of the combustion exhaust E exceeds 69 (° C.). If the regulated flow rate is reduced from 31 (L) to 26 (L), the proportional valve 48 is narrowed maintaining the outgoing hot water temperature, and the combustion capacity is suppressed, the temperature of the combustion exhaust E can be moved to be equal to or below 69 (° C.). In this case, the opening of the proportional valve 48 may be narrowed to reduce the maximum combustion capacity of the burner 36 directly. If the outgoing hot water temperature is tried to be maintained, the flow rate of supplied hot water results in decreasing.
- the temperature of the combustion exhaust E can be regulated equal to or below 69 (° C.).
- this control of the exhaust temperature is realized by the combustion control maintaining the combustion of a burner.
- a material of low heat-resistance can be used for an exhaust system such as the exhaust path 10 . Therefore, a part or all of the exhaust system such as the exhaust path 10 can be composed of a material of low heat-resistance, for example, synthetic resin.
- the air supply A 2 is mixed with the combustion exhaust E, whose temperature is lowered by secondary heat exchange, using the exhaust dilution fan 100 , and the temperature of the combustion exhaust E flowing into the exhaust tube 34 is lowered so that a material of low heat-resistance such as a resin duct can stand heat.
- the air supply A 2 is mixed with the combustion exhaust E after heat exchange, and the air supply A 2 is prevented from flowing into the secondary heat exchanger 40 at the downstream side.
- the exhaust temperature of the combustion exhaust E can be efficiently lowered without reducing the heat exchange efficiency of the secondary heat exchanger 40 .
- the control of the exhaust temperature is disclosed that the combustion is reduced to lower the temperature of the combustion exhaust E.
- This third embodiment discloses that the temperature of the combustion exhaust E is lowered by dilution air from the exhaust dilution fan 100 .
- FIG. 10 depicts an example of processing procedure of an exhaust temperature control process according to the third embodiment.
- the processing procedure is an example of the present invention, and includes a process that the rotation speed of the exhaust dilution fan 100 is increased maintaining the volume of the combustion, and dilution air is increased to lower the exhaust temperature.
- the processing procedure is executed in the above described water heater 6 .
- step S 201 If the detected temperature of the combustion exhaust E is equal to or over 69 (° C.) (step S 201 ), whether “gou” is equal to or over 20 (gou), or not is determined (step S 202 ). If “gou” is equal to or over 20 (gou) (YES of step S 202 ), reduction of “gou” is executed (step S 203 ) as well as the second embodiment, and the procedure returns to the process like the second embodiment.
- step S 202 If “gou” is below 20 (gou) (NO of step S 202 ), the rotation speed of the exhaust dilution fan 100 is increased (step S 204 ), and the procedure returns to the process like the second embodiment.
- the rotation speed of the exhaust dilution fan 100 maybe increased. By increasing the rotation speed of the exhaust dilution fan 100 and increasing the air supply A 2 to be mixed with the combustion exhaust E, the temperature of the combustion exhaust E can be lowered with the air supply A 2 .
- the combustion exhaust E (the volume of exhaust) results in increasing.
- a reference value is set for “gou”.
- 20 (gou) is set for a threshold level, and “gou” is over 20 (gou), reduction of “gou” is executed. If “gou” is below 20 (gou), the volume of dilution air is increased.
- the exhaust temperature of the combustion exhaust E can be lowered by increasing the rotation speed of the exhaust dilution fan 100 .
- the flow rate may be decreased when the used hot water supply capability is high, and the rotation speed of the exhaust dilution fan 100 may be increased when the capability is low.
- the control according to the hot water supply capacity of the water heater 6 can be realized, and the convenience can be improved.
- the combustion fan 42 and the exhaust dilution fan 100 may be rotated in the minimum rotation speed when the exhaust temperature is high while the combustion is stopped or during the detection of the exhaust Hi limit 106 .
- the operation of the combustion fan 42 and the exhaust dilution fan 100 may be determined as depicted in FIGS. 11 and 12 . According to the control using the detected temperatures of the hot water temperature sensor 88 at the outlet of the heat exchanger 38 , the temperature detected by the exhaust temperature sensor 108 and a switching output of the exhaust Hi limit 106 like the above, freezing can be prevented.
- the backflow preventer 102 has the structure that opening and closing positions are automatically determined according to wind pressure in the above embodiments.
- the contrary wind CW acting on the backflow preventer 102 may be detected, and the opening and closing of the backflow preventer 102 may be controlled electrically by detected wind pressure and the wind pressure from the air supply A 2 .
- the exhaust dilution duct 96 is set short and the exhaust dilution fan 100 is placed in the vicinity of the exhaust dilution unit 32 in the above embodiments, the inventions are not limited thereto. As depicted in FIG. 13 , the exhaust dilution duct 96 may be arranged in parallel to the combustion chamber 28 , and the height of the exhaust dilution fan 100 may be brought to the same as the combustion fan 42 .
- the fuel gas G is exemplified as fuel in the above embodiments.
- Fuel is not limited to gas, and may be liquid.
- the place for introducing (mixing) dilution air by the dilution fan is made to join the exhaust outlet of the combustion air at the downstream side of the heat exchangers, for diluting the combustion air.
- a backflow preventer may be built in so as to be used for extended exhaust pipe.
- An exhaust temperature sensor monitoring an exhaust temperature may be placed at the exhaust outlet, and dilution fan rotating control means or combustion control means may be provided.
- a dilution fan and a dilution path from the dilution fan to the exhaust outlet may be placed at a proper place in the housing, and the mixture part with the combustion exhaust may be provided so as not to prevent combustion exhaust.
- the exhaust Hi limit 106 is used for the detection of the exhaustion temperature.
- the inventions are not limited thereto. Operation characteristics of the exhaust Hi limit 106 may be realized by a plurality of the exhaust temperature sensors that when the temperature of the combustion exhaust E reaches the upper temperature limit, conduction is switched to non-conduction when the temperature of the combustion exhaust E drops to the lower temperature limit, non-conduction is switched to conduction.
Abstract
Description
- 1. Field of the Invention
- The present invention relates to exhaust control of a combustion apparatus such as a heat pump recovering latent heat from combustion exhaust and, for example, relates to a combustion apparatus, a method for combustion control, a combustion control board, a combustion control system and a water heater that control a temperature of exhaust gas to be a predetermined temperature or below.
- 2. Description of the Related Art
- Higher efficiency of heat exchange of combustion exhaust can be achieved if sensible heat of the combustion exhaust of high temperatures is exchanged (primary heat exchange) and latent heat of the combustion exhaust after the primary heat exchange is exchanged (secondary heat exchange). However, water vapor in the air is condensed around a secondary heat exchanger by its heat exchange of the latent heat of the combustion exhaust after the primary heat exchange, and thus drains are generated.
- It is known concerning the above heat exchange of combustion gas that when drains are generated around a heat exchanger, combustion gas is diluted by supplying air to the periphery of the heat exchanger and when drains are not generated, air feeding pipes are cooled and thus, the occurrence of drains and white smoke in an exhaust path etc. is prevented (for example, Japanese Laid-open Patent Publication No. 05-312412).
- It is known concerning reduction of white smoke that NOx is reduced by an induction fan, provided for a dilution air hole and introducing dilution air from the dilution air hole, provided for an exhaust gas flow path, to the exhaust gas flow path, and discharging white smoke is prevented by diluting and lowering the temperature of exhaust gas with saturated water vapor (for example, Japanese Laid-open Patent Publication No. 2000-291940.)
- It is also known that if a plurality of latent heat recovery type heat pumps are provided, combustion exhaust gases from an individual passage of each of the latent heat recovery type heat pump are mixed to reduce white smoke (for example, Japanese Laid-open Patent Publication No. 2001-241641.)
- It is known concerning exhaust control of combustion equipment that combustion capacity is controlled in response to an exhaust temperature to lower the exhaust temperature (for example, Japanese Laid-open Patent Publication No. 2009-121814.)
- In the art of supplying air from air feeding pipes to dilute combustion gas around a heat exchanger, the air is blown to the heat exchanger installed downstream of exhaust. There occurs the inconvenience that the air cools water feeding pipes of the heat exchanger to decrease heat efficiency.
- In the art of introducing dilution air to an exhaust gas flow path to dilute exhaust gas, pressure fluctuation occurs at the downstream of combustion means if combustion conditions vary and exhaust gas emissions vary. Pressure suppression is needed since the supply of mixture gas by an induction fan for combustion or an air ratio varies.
- When the occurrence of white smoke is suppressed by mixing dilution air with combustion exhaust gas, a fan for dilution is installed outside equipment after the equipment is installed. In this case, some technique to install the fan is needed and thus, it is difficult to apply the art to equipment for an extended exhaust pipe.
- The art of controlling exhaust temperatures by controlling combustion capacity in response to the exhaust temperatures is for in-room installation, and not suitable for outdoor installation.
- A first object of the present invention is to achieve lower temperatures of combustion exhaust after heat exchange without decreasing heat efficiency of the heat exchange.
- A second object of the present invention is to select materials used for an exhaust path more freely by lowering an exhaust temperature.
- A third object of the present invention is to achieve minimizing an apparatus, that is, a compact apparatus by diluting combustion exhaust.
- To achieve the above objects, a combustion apparatus of the present invention includes combustion means generating combustion exhaust by combustion of fuel; heat exchange means exchanging heat of the combustion exhaust; and exhaust dilution unit supplying dilution air after the heat exchange by the heat exchange means and diluting the combustion exhaust after the heat exchange.
- To achieve the above objects, a method for combustion control of the present invention includes generating combustion exhaust by combustion of fuel; exchanging heat of the combustion exhaust; and supplying dilution air after the heat exchange of the combustion exhaust and diluting the combustion exhaust after the heat exchange.
- To achieve the above objects, a combustion control board of the present invention includes a control unit taking a detected temperature of combustion exhaust, generating an output of stopping combustion if the detected temperature is equal to or over an upper temperature limit, and generating a control output permitting the combustion if the detected temperature reaches a lower temperature limit.
- To achieve the above objects, a combustion control system of the present invention includes combustion means generating combustion exhaust by combustion of fuel; heat exchange means exchanging heat of the combustion exhaust; exhaust dilution unit supplying dilution air after the heat exchange by the heat exchange means and diluting the combustion exhaust after the heat exchange; and control means stopping combustion by the combustion means if the temperature of the combustion exhaust is equal to or over an upper temperature limit, and permitting the combustion if the temperature of the combustion exhaust is equal to or below a lower temperature limit.
- To achieve the above objects, a water heater of the present invention includes combustion means generating combustion exhaust by combustion of fuel; heat exchange means exchanging heat of the combustion exhaust for water; and exhaust dilution unit supplying dilution air after the heat exchange by the heat exchange means and diluting the combustion exhaust after the heat exchange.
- Any of the following effects can be obtained from the above described combustion apparatus, method for combustion control, combustion control board, combustion control system or water heater of the present invention.
- (1) Excess air does not flow in a heat exchanger since combustion gas is diluted in a place following a place of exchanging heat. Thereby, heat efficiency is not decreased.
- (2) Dilution fan control and combustion control are executed as well as exhaust temperature control can be executed, by monitoring exhaust temperatures any time. Even if a contrary wind occurs, a backflow preventer works and an exhaust obstruction occurs, it is possible to find the change of exhaust temperatures and stop combustion.
- (3) Diluting and cooling exhaust brings more choice of materials for exhaust paths. For example, a resin damper can be manufactured.
- (4) Minimizing an apparatus, that is, a compact apparatus can be achieved even if dilution means is provided.
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FIG. 1 depicts an example of a water heating system according to a first embodiment; -
FIG. 2 depicts an example of a water heater according to a second embodiment; -
FIG. 3 is an enlarged view of a combustion chamber; -
FIG. 4 is an enlarged view of an air supply tube and an exhaust dilution unit; -
FIGS. 5A to 5B depict an example of structure of a backflow preventer and operation thereof; -
FIGS. 6A to 6B depict an example of structure of an exhaust Hi limit and operation thereof; -
FIGS. 7A to 7C depict an example of structure of the exhaust Hi limit and operation thereof; -
FIG. 8 depicts an example of an electric board; -
FIG. 9 is a flowchart depicting an example of processing procedure of exhaust temperature control; -
FIG. 10 is a flowchart depicting an example of processing procedure of exhaust temperature control according to a third embodiment; -
FIG. 11 depicts an example of a control form of a combustion fan and an exhaust dilution fan according to other embodiments; -
FIG. 12 depicts an example of a control form of the combustion fan and the exhaust dilution fan according to the other embodiments; and -
FIG. 13 depicts an example of a water heater according to the other embodiments. - A first embodiment discloses a water heating system. The first embodiment will be described with reference to
FIG. 1 .FIG. 1 depicts an example of a water heating system. - A
water heating system 2 is an example of a combustion apparatus, a method for combustion control, a combustion control board, a combustion control system or a water heater of the present invention. Thewater heating system 2 is installed in aroom 4, and, as depicted inFIG. 1 , provides awater heater 6, anair supply path 8 and anexhaust path 10. - The
water heating system 2 is an example of a combustion system combusting fuel gas G. Thewater heating system 2 is a system for exchanging heat of combustion exhaust for water to supply the heated water. - The
room 4 is an example of a room separated from a living space, and may be a space closed to the outside air such as a garage. Awall 12 and aceiling 14 are separation means separating thewater heating system 2 from the outside air. 16 is an indoor space. - The
water heater 6 is an example of a combustion apparatus combusting the fuel gas G, and has a function of exchanging heat of combustion exhaust for water to supply the heated water. Thewater heater 6 may be a latent heat recovery type water heater. Thewater heater 6 may provide a latent heat recovery type heat pump, and may provide a plurality of latent heat recovery type heat pumps for a hybrid product such as a water heater with space heating capability and a bath water heater. - The
air supply path 8 is an example of air supply means for thewater heater 6, and installed between an air supply part (for example, a sidewall vent) 18 placed in thewall 12 and thewater heater 6. Astay rod 20 is provided for theair supply path 8 at its middle. In the embodiment, thestay rod 20 fixes theair supply path 8 to theceiling 14. - The
exhaust path 10 is an example of exhaust means from thewater heater 6, and is installed between an exhaust part (terminator) 22 placed in thewall 12 and thewater heater 6. Astay rod 24 is provided for theexhaust path 10 at its middle. In the embodiment, thestay rod 24 fixes theexhaust path 10 to theceiling 14. - The
air supply part 18 and theexhaust part 22 are placed separately from each other to prevent combustion exhaust from being supplied into theair supply part 18. - In the
water heating system 2 like the above, air is taken from the outside into theair supply part 18, the taken air is introduced to thewater heater 6 through theair supply path 8, and thus combustion of the fuel gas G is supported. Combustion exhaust generated in thewater heater 6 is introduced from theexhaust path 10 to theexhaust part 22 to be vented outside the room. - A second embodiment discloses the above described
water heater 6. The second embodiment will be described with reference toFIGS. 2 and 3 .FIG. 2 depicts an example of a water heater andFIG. 3 depicts an enlarged combustion chamber of the water heater. - The
water heater 6 is an example of a combustion apparatus of the present invention. Thewater heater 6 exchanges heat of combustion exhaust for water W to supply hot water HW. Ahousing 26 is provided for thewater heater 6. Acombustion chamber 28 is placed in thehousing 26. Thehousing 26 is a sealed space. Anair supply tube 30 is formed on thehousing 26 for supplying air into the sealed space. The above describedair supply path 8 is connected to theair supply tube 30, and air supply A is executed via theair supply tube 30 and theair supply path 8. - The
combustion chamber 28 is a combustion space. Anexhaust dilution unit 32 is provided for thecombustion chamber 28 on its top. Anexhaust tube 34 is formed on theexhaust dilution unit 32. Theexhaust tube 34 is separated from the sealed space of thehousing 26. The above describedexhaust path 10 is connected to theexhaust tube 34, and exhaust E is vented via theexhaust tube 34 and thecombustion exhaust path 10. Aburner 36, aprimary heat exchanger 38 and asecondary heat exchanger 40 are placed in thecombustion chamber 28. - The
burner 36 is an example of combustion means combusting fuel gas G, and provides afirst burner unit 362, asecond burner unit 364 and athird burner unit 366. Aguide 367 surrounding theseburner units partition 369 between theburner unit 362 and theburner unit 364, and apartition 370 between theburner unit 364 and theburner unit 366 respectively partition a space for the burner units into an individual space. - A
combustion fan 42 is placed below theburner units combustion fan 42 from the air A supplied into thehousing 26. Amain valve 46, aproportional valve 48 andchangeover valves gas supply pipe 44 that supplies the fuel gas G to theburner 36 as means supplying and adjusting the supply of the fuel gas G, or closing the supply thereof. Themain valve 46 is placed most upstream of thegas supply pipe 44, and is a changeover valve for supplying or closing the supply of the fuel gas G. Theproportional valve 48 adjusts the supply of the fuel gas G of flowing in thegas supply pipe 44. Thechangeover valves burner units burner units gas supply inlet 55 of thegas supply pipe 44, and the fuel gas G is supplied therefrom. - A spark plug 56, a flame detection rod 58 and a self-check flame rod 60 are provided for a combustion outlet of the
burner 36. Anigniter 62 placed outside thecombustion chamber 28 is connected to the spark plug 56. - The
primary heat exchanger 38 is an example of a first heat exchange means, is placed upstream of combustion exhaust E generated by the combustion of theburner 36, and mainly exchanges sensible heat from the combustion exhaust E for the water W. - The
secondary heat exchanger 40 is an example of a second heat exchange means, is placed more downstream than theprimary heat exchanger 38, and mainly exchanges latent heat from the combustion exhaust E after the primary heat exchange for the water W.A drain vessel 64 is placed below thesecondary heat exchanger 40. Thedrain vessel 64 receives drain (waste field) D generated in thesecondary heat exchanger 40 by secondary heat exchange. Adrainpipe 66 is connected to thedrain vessel 64. The drain D received by thedrain vessel 64 is introduced through thedrainpipe 66 to a drain outlet 68 of thehousing 26 to be discharged. - A
water supply path 70 is connected to thesecondary heat exchanger 40, and the water W is supplied to thesecondary heat exchanger 40 prior to theprimary heat exchanger 38. A tap water path is connected to awater supply inlet 71 of thewater supply path 70, and the water W such as tap water is supplied therefrom. The inlet of theprimary heat exchanger 38 is linked to the outlet of thesecondary heat exchanger 40 by ajoint path 72, and the hot water HW obtained by the secondary heat exchange flows into theprimary heat exchanger 38 via thejoint path 72. Ahot water path 74 is connected to the outlet of theprimary heat exchanger 38, and the hot water HW heated by the primary heat exchange flows into thehot water path 74. Abypath circuit 76 across theprimary heat exchanger 38 is provided between thewater supply path 70 and thehot water path 74. Thebypath circuit 76 is means for running the water W into the hot water HW. Abypath valve 78 is placed at the inlet of the bypath circuit 76 (water supply path 70 side). The flow rate of the water W supplied to the hot water HW via thebypath circuit 76 is determined according to the opening of thebypath valve 78. Aflow rate sensor 79 is placed in thewater supply path 70 for detecting the flow rate. Awater control valve 82 is placed between thehot water path 74 and a hotwater supply path 80. The flow rate of the outgoing hot water HW is controlled according to the opening of thewater control valve 82 and thus, the supply of the water W is controlled. - A
temperature sensor 84 is placed at thewater supply path 70, and detects the temperature of supplied water. A heat exchange Hi limit 86 and a hotwater temperature sensor 88 are placed at the outlet of theprimary heat exchanger 38, and the temperature of the hot water HW is detected. Amixture temperature sensor 90 is placed at the hotwater supply path 80, and detects the temperature of the mixture of the hot water HW and the water W. The heat exchange Hi limit 86 is the same structure as an exhaust Hi limit 106 (FIG. 6 ) described below. - A hot
water supply pipe 93 supplying hot water to a demanded place such as a house's interior is connected to ahot water outlet 91 of the hotwater supply path 80, and ahot water faucet 95 is provided thereto. Thehot water faucet 95 may be a shower valve. - The
exhaust dilution unit 32 is formed on the top of thecombustion chamber 28, is an exhaust path bent by afirst path wall 92 and asecond path wall 94, and provides anexhaust dilution duct 96 on the top of thecombustion chamber 28. Theexhaust dilution duct 96 communicates with apath 98 surrounded by thepath walls exhaust dilution fan 100 is placed at theexhaust dilution duct 96, and air supply A2 from thehousing 26 is taken into thepath 98 through theexhaust dilution duct 96 by theexhaust dilution fan 100. The air supply A2 is mixed with the combustion exhaust E, and the combustion exhaust E is diluted by the air supply A2. The combustion exhaust E after the dilution flows into theexhaust path 10 from theexhaust tube 34. Abackflow preventer 102 and apartition 104 are placed in theexhaust dilution duct 96 as air flow guides. Thebackflow preventer 102 is an example of backflow preventing means that prevents the combustion exhaust E from flowing back to theexhaust dilution fan 100. Thepartition 104 prevents the air supply A2 from intruding into thesecondary heat exchanger 40. - The exhaust Hi limit 106 (
FIG. 6 ) and anexhaust temperature sensor 108 are placed at theexhaust dilution unit 32. The exhaust Hi limit 106 is an example of a temperature detection switch. The exhaust Hi limit 106 monitors the temperature of the combustion exhaust E and if 69 (° C.) is detected as a predetermined temperature, theexhaust Hi limit 106 becomes non-conducts. Theexhaust temperature sensor 108 is an example of a temperature sensor detecting an exhaust temperature. - An
electric board 110 is placed in thehousing 26. Theelectric board 110 is electric control means for thewater heater 6 and is an example of a combustion control board. Anelectrical supply line 112 is connected to theelectric board 110, and an AC source is inputted via asurge box 114, atransformer 116 andGFI 118. Thesurge box 114 is means for absorbing a surge from an AC source and thetransformer 116 transforms an AC source to a predetermined voltage. - As to the
water heater 6, described will be (a) a start of water heating and combustion operation, (b) heat exchange operation, (c) exhaust dilution operation of theexhaust dilution unit 32, (d) air supply and exhaust operation, (e) hot water outgoing temperature control, (f) combustion control of theburner 36 and (g) drain discharge operation. - (a) Start of Water Heating and Combustion Operation
- In the
water heater 6, when the hotwater supply faucet 95 of a shower etc. connected to the hotwater supply path 80 is opened, the water W flows into thewater supply path 70. In thewater supply path 70, the temperature of supplied water is detected by thetemperature sensor 84 and the flow rate of supplied water is detected by thewater rate sensor 79. The detected information is inputted to theelectric board 110. Themain valve 46 is opened, thechangeover valve burner 36 is ignited by the operation of theigniter 62 and the spark plug 56. At that time, thecombustion fan 42 starts working, and combustion air (the air supply A1) is supplied to theburner 36 from the air supply A supplied from theair supply tube 36 to thehousing 26. The fuel gas G mixed with the air supply A1 is combusted in theburner 36. This combustion generates the combustion exhaust E of high temperatures in thecombustion chamber 28. - (b) Heat Exchange Operation
- The combustion exhaust E flows into the
primary heat exchanger 38 at a downstream side assuming that theburner 36 in thecombustion chamber 28 is upstream. In theprimary heat exchanger 38, sensible heat is mainly absorbed from the combustion exhaust E to be exchanged for the water W (primary heat exchange). The combustion exhaust E after the primary heat exchange flows into thesecondary heat exchanger 40. In thesecondary heat exchanger 40, latent heat is mainly absorbed from the combustion exhaust E after the primary heat exchange to be exchanged for the water W (secondary heat exchange). Like the above, the combustion exhaust E after the primary heat exchange and the secondary heat exchange is cooled with its sensible heat and latent heat being absorbed, diluted by being mixed with the air supply A2 by theexhaust dilution unit 32 to be further cooled, and then vented to the outside through theexhaust tube 34 and theexhaust path 10. - (c) Exhaust Dilution Operation of
Exhaust Dilution Unit 32 - The
exhaust dilution fan 100 starts rotating at the same time when theburner 36 starts combusting, and thebackflow preventer 102 at theexhaust dilution duct 96 is opened. If theexhaust dilution fan 100 rotates, the air A2 is sent from thehousing 26 to theexhaust dilution duct 96, and the air A2 is supplied from theexhaust dilution duct 96 to theexhaust dilution unit 32. The air A2 joins the combustion exhaust E after the secondary heat exchange, the combustion exhaust E is diluted by the air supply A2, and thus the combustion exhaust E after the secondary heat exchange is further cooled. - The temperature of the combustion exhaust E in the
exhaust dilution unit 32 is monitored by theexhaust Hi limit 106 and theexhaust temperature sensor 108. When the exhaust temperature exceeds a setting temperature of theexhaust Hi limit 106, for example, 69 (° C.), theexhaust Hi limit 106 becomes non-conducts. Thereby, the temperature of the combustion exhaust E is lowered by the control of the combustion of theburner 36 etc. - (d) Air Supply and Exhaust Operation
- Air is supplied from the outside to the
water heater 6 via theair supply pipe 8, and the combustion exhaust E is vented to the outside via theexhaust path 10. The rotation of theexhaust dilution fan 100 is associated with that of thecombustion fan 42. If the rotation speed of thecombustion fan 42 is reduced, the rotation speed of theexhaust dilution fan 100 is reduced. On the contrary, if the rotation speed of thecombustion fan 42 is increased, the rotation speed of theexhaust dilution fan 100 is also increased. As the above, the rotation of theexhaust dilution fan 100 andcombustion fan 42 may be associated and may be independent. - (e) Hot Water Outgoing Temperature Control
- The water W flows into the
secondary heat exchanger 40. After heat exchange is executed with latent heat of the combustion exhaust E at the downstream side (secondary heat exchange), the water W flows into theprimary heat exchanger 38, and then heat exchange is executed with sensible heat of the combustion exhaust E at the upstream side (primary heat exchange). The temperature of the hot water HW in the outlet of theprimary heat exchanger 38 is detected by the hotwater temperature sensor 88 at the outlet of theprimary heat exchanger 38. When the detected temperature is higher than a target temperature, thebypath valve 78 is opened, the water W flows into thebypath circuit 76 to be mixed with the hot water HW, and the temperature of the hot water HW is controlled to be the target temperature. The temperature of the hot water HW is detected by themixture temperature sensor 90 at the hotwater supply path 80. The hot water HW is supplied to the above described shower etc. - The temperatures detected by the
mixture temperature sensor 90 are inputted to theelectric board 110 continuously, and is used for the opening control of thewater control valve 82 as control information. As a result, the flow rate is controlled to be a flow rate necessary to reach the target temperature by the opening of thewater control valve 82. Based on the flow rate, the hot water HW is supplied from the hotwater supply path 80. - (f) Combustion Control of
Burner 36 - In the
burner 36, theburner units burner 36 are switched by the opening and closing of thechangeover valves main valve 46 at thegas supply pipe 44 is open, and the supply of the fuel gas G is adjusted according to the opening of theproportional valve 48 to control the combustion of the fuel gas G. - (g) Drain Discharge Operation
- In the
secondary heat exchanger 40 recovering latent heat of the combustion exhaust E, water vapor in the combustion exhaust E is condensed by heat exchange, and the drain D is generated. The drain D includes impurities in the combustion exhaust E. The drain D is pooled in thedrain vessel 64 placed below thesecondary heat exchanger 40, introduced from thedrain 66 to the drain outlet 68, and discharged to the outside of thewater heater 6. - The
exhaust dilution unit 32 will be described with reference toFIGS. 4 to 6B .FIG. 4 depicts the mixture of combustion exhaust and dilution air in the exhaust dilution part,FIGS. 5A to 5B depict a function of the backflow preventer, andFIGS. 6A to 6B depict the structure of the exhaust Hi limit and operation thereof. InFIGS. 4 to 6B , the same components as those inFIGS. 2 to 3 are denoted by the same reference numerals. - The
exhaust dilution unit 32 is means for mixing the air A2 with the combustion exhaust E after heat exchange, diluting the combustion exhaust E by the air A2, and lowering the temperature of the combustion exhaust E further than that after the heat exchange. - The combustion exhaust E, whose sensible heat is absorbed by the heat exchange in the
primary heat exchanger 38 and whose latent heat is absorbed by the heat exchange in thesecondary heat exchanger 40, lowers its temperature to 80 (° C.) (176 (° F.)) or so. However, although theexhaust pipe 10 can stand the heat of the temperature if a metal tube is used therefore, if a resin tube is used for theexhaust pipe 10, it is needed to lower the temperature of the combustion exhaust E below heat proof temperature of the resin. Thus, it is needed that the temperature of the combustion exhaust E passing through theexhaust dilution unit 32 is lowered below 69 (° C.) (156 (° F.)). In the CSA (Canadian Standard Association) standard, it is required that the temperature of the combustion exhaust E of the maximum combustion is 69 (° C.) (156(° F.)) or below (° C.=(° F.−32)×5/9). - The
exhaust dilution unit 32 is placed in order to apply to such standard. Theexhaust dilution unit 32 is a function unit taking the air A2 of the room temperature thereinto by rotating theexhaust dilution fan 100, diluting the combustion exhaust E by mixing the air A2 with the combustion exhaust E, and cooling combustion exhaust E to equate or lower the temperature of the combustion exhaust E flowing in theexhaust tube 34 to or below the standard temperature. - In the embodiment, as depicted in
FIG. 4 , theexhaust dilution unit 32 is placed downstream of thecombustion chamber 28. Theexhaust dilution duct 96 is provided for theexhaust dilution unit 32. Theexhaust dilution fan 100 is provided for theexhaust dilution duct 96 to take the air A2. The air A2 is efficiently mixed with the combustion exhaust E after the secondary heat exchange by providing thebackflow preventer 102 and thepartition 104. Describing the mixture of the air A2 with the combustion exhaust E in detail, theexhaust dilution fan 100 rotates, the air A2 is taken from the inside space of thehousing 26 into theexhaust dilution duct 96, thebackflow preventer 102 is opened, and thepartition 104 guides an air flow. As a result, the combustion exhaust E passing through thesecondary heat exchanger 40 is taken into the air supply A2 guided by thepartition 104 to be joined, and the air A2 is mixed with the combustion exhaust E. - The
partition 104 guides the air A2 to introduce the air A2 to thepath wall 92 and thus, the air A2 joins the combustion exhaust E reaching thepath 92 without preventing the combustion exhaust E at thesecondary heat exchanger 40 from rising. Such an air flow guiding function of thepartition 104 efficiently mixes the combustion exhaust E and the air A2, and prevents the air A2 from flowing into thesecondary heat exchanger 40. Thus, thesecondary heat exchanger 40 does not touch the air A2, and the decrease of the efficiency of the heat exchange of thesecondary heat exchanger 40 can be prevented. - The
backflow preventer 102 placed at the inlet of theexhaust dilution duct 96 prevents the combustion exhaust E from flowing back to theexhaust dilution fan 100 to prevent the combustion exhaust E from being mixed with the air A1. If there is nobackflow preventer 102 and a contrary wind occurs, the outlet of theexhaust dilution fan 100 is shut to cause the combustion exhaust E to flow back to the air supply outlet of theexhaust dilution fan 100. If the combustion exhaust E flows into the space of thehousing 26, the combustion exhaust E is absorbed into thecombustion fan 42, and combustion failure of theburner 36 is generated by the exhaust obstruction. This is exhaust recycling by a backflow of the combustion exhaust E. - If a backflow of the combustion exhaust E is generated, the occurrence of the above described exhaust recycling is prevented by closing the
backflow preventer 102. In this case, if thebackflow preventer 102 is closed, the temperature of the combustion exhaust E in theexhaust dilution unit 32 increases since the air A2 is not supplied to theexhaust dilution duct 96. This increase of the temperature is detected by theexhaust temperature sensor 108. The temperature detected by theexhaust temperature sensor 108 is informed to theelectric board 110 rapidly. As a result, combustion control that the combustion of theburner 36 is immediately decreased is performed. Like the above, the occurrence of the combustion failure due to the backflow of the combustion exhaust E can be prevented and the temperature rising in theexhaust dilution unit 32 can be surely prevented by adjusting the combustion. - The
backflow preventer 102 is an example of backflow preventing means. As depicted inFIG. 5A , thebackflow preventer 102 is rotatably supported at the outlet of theexhaust dilution fan 100 by ahinge 101, and opens and closes theexhaust dilution duct 96 by the force of wind (wind pressure). If theexhaust dilution fan 100 is operated, the air supply A2 is generated. Thebackflow preventer 102 is opened in response to the air supply A2 and the air supply A2 flows into theexhaust dilution duct 96. If theexhaust dilution fan 100 stops, thebackflow preventer 102 restores a closed position by its own weight as depicted in dashed lines. - If a contrary wind CW of higher wind pressure than the air supply A2 acts on the
exhaust dilution duct 96, as depicted inFIG. 5B , thebackflow preventer 102 is pushed back to its closed position by the contrary wind CW. As a result, it can be prevented for the contrary wind CW to run into theexhaust dilution fan 100. - The exhaust Hi limit 106 is, as depicted in
FIG. 6A , a temperature detection switch including atemperature detection part 107 and opening andclosing contact 109. Thetemperature detection part 107 may be made of a bimetal. The opening andclosing contact 109 is a contact opened and closed by a bimetal. In theexhaust Hi limit 106, as depicted inFIG. 6B , switching operation of a hysteresis characteristic is obtained. If thetemperature detection part 107 detects an upper temperature limit H=69 (° C.), the opening andclosing contact 109 is switched from a closed state (conducting) to an opened state (non-conducting). After the upper temperature limit H=69 (° C.) is detected, the opening andclosing contact 109 is kept opened till thetemperature detection part 107 detects a lower temperature limit L=55 (° C.). After the temperature reaches the lower temperature limit L=55 (° C.), the opening andclosing contact 109 is switched to closed. - The exhaust Hi limit 106 will be described with reference to
FIGS. 7A to 7C .FIG. 7A depicts the principle of the temperature detection part of the exhaust Hi limit, andFIGS. 7B and 7C depict switching structure of the exhaust Hi limit and the operation thereof. - A bimetal 136 is used for the
temperature detection part 107 as depicted inFIG. 7A that is made by uniting a highexpansion coefficient metal 132 presenting high expansion by heating and a lowexpansion coefficient metal 134 of lower expansion than the highexpansion coefficient metal 132. The bimetal 136 is supported so as to be able to change the position of its ends. The position thereof is changed from that depicted by solid lines before heating to that depicted by broken lines after heating. - The exhaust Hi limit 106 is a sensing temperature switch providing the bimetal 136 at the
temperature detection part 107. Apin 138 touching its end to the bimetal 136 is movably held by aretainer 140 in the exhaust Hi limit 106 as depicted inFIG. 7B . Aspring 144 is inserted between another end of thepin 138 and acase 142. Restoring force of thespring 144 acts. A fixingcontact 146 is attached to afixing piece 145 fixed to thecase 142. Amovable contact 148 is attached to thespring 144. - Before heating, as depicted in
FIG. 7B , themovable contact 148 touches the fixingcontact 146 to maintain a closed state (a state of the opening andclosing contact 109 depicted by solid lines inFIG. 6A ). After heating, as depicted inFIG. 7C , themovable contact 148 separates from the fixingcontact 146 since thepin 138 receiving the change of the bimetal 136 drops down to compress the spring 144 (a state of the opening andclosing contact 109 depicted by broken lines inFIG. 6A ). Like the above, a temperature is detected and opening and closing of the fixingcontact 146 and themovable contact 148 is realized. - A
cap 152 is attached to the top of thecase 142 intervening aspacer 150 between thecap 152 and theretainer 140. Thecase 142 is provided with anattachment 154. A terminal 156 is placed at the bottom of thecase 142. The terminal 156 is connected to themovable contact 148 in thespring 144, and a different terminal is provided for the fixingcontact 146 in the fixingpiece 145. Therefore, thecase 142 is fixed to an outer wall of thedilution exhaust unit 32 by theattachment 154, and an output by the opening and closing of the fixingcontact 146 and themovable contact 148 based on temperature detection can be obtained. - A control system of the
water heater 6 will be described with reference toFIG. 8 .FIG. 8 depicts an example of the structure of an electric board. InFIG. 8 , the same components as those inFIGS. 2 to 4 are denoted by the same reference numerals. - The
electronic board 110 is an example of a combustion control board or a combustion control system of the present invention, and provides acontrol unit 120. Thecontrol unit 120 is an example of control means, maybe composed of a microcomputer, and, for example, provides a CPU (Central Processing Unit) 122, a ROM (Read-Only Memory) 124, a RAM (Random-Access Memory) 126, an input/output unit (I/O) 128 and atimer 130. - The
CPU 122 is an example of calculation means executing various calculation, determining means for detection information and control means for generating a control output etc. TheCPU 122 executes a control program in theROM 124 and generates a control output based on combustion control on the basis of a flame determination result, detected temperatures, detected flow rates, etc. TheROM 124 is an example of storage means storing a control program etc. TheRAM 126 composes an execution area of a program. The I/O 128 is an example of an input unit taking detection information etc. and an output unit outputting a control output to various function units. Thetimer 130 is an example of time keeping means and measures combustion time etc. - Start and stop information on driving is inputted from a driving
switch 121 to thecontrol unit 120 of theelectric board 110. As detection information, flow rate information is inputted from theflow rate sensor 79 to thecontrol unit 120 and temperature information etc. are inputted from thetemperature sensor 84, the hotwater temperature sensor 88, themixture temperature sensor 90 and theexhaust Hi limit 106 to thecontrol unit 120. Rotating speed information etc. is inputted from thecombustion fan 42 and theexhaust dilution fan 100 of the air supply unit is also inputted to thecontrol unit 120. Information whether there is FR current or not and information on current measured value as flame detection information from a flame rod are also inputted to theelectric board 110. - Control information based on the input information is outputted to the
combustion fan 42, theexhaust dilution fan 100, themain valve 46, theproportional valve 48, thechangeover valves water control valve 82, theigniter 62 andother function units 63. Theother function units 63 may include informingmeans 65 such as a speaker, a buzzer and a display. - An example of exhaust temperature control using the
electric board 110 will be described. This temperature control of the combustion exhaust E is realized by controlling the volume of combustion or flow rate of outgoing hot water according to the temperature detected by theexhaust temperature sensor 108 while the combustion is maintained. Since the amount of the combustion (the fuel supply rate) and the flow rate of outgoing hot water are linked, the fuel supply rate may be adjusted or the flow rate of outgoing hot water may be adjusted. - (1) Control of Combustion
- When the temperature of the combustion exhaust E is equal to or over the upper temperature limit H, the maximum combustion capacity (unit used in Japan: “gou”) is gradually reduced. When the temperature of the combustion exhaust E is lowered to the lower temperature limit L, the maximum combustion capacity (“gou”) is gradually increased. Thereby, the temperature of the combustion exhaust E is controlled to be within predetermined temperatures. In this case, the temperature of outgoing hot water is kept in setting temperatures. The range of “gou” (1 to 5 (gou)) maybe changed according to the temperature of the combustion exhaust E as another way.
- (2) Flow Rate Control of Outgoing Hot Water
- When the temperature of the combustion exhaust E is equal to or over the upper temperature limit H, the flow rate of outgoing hot water is reduced by narrowing the opening of the
water control valve 82. When the temperature of the combustion exhaust E reaches the lower temperature limit L, the flow rate of outgoing hot water is increased by the degree of the opening of thewater control valve 82. Thereby, as well, the temperature of the combustion exhaust E is controlled to be within predetermined temperatures. In this case, the temperature of outgoing hot water is also kept in setting temperatures. - In this case, since the flow rates of outgoing hot water and those of supplied water are the same, “gou” can be adjusted by regulating or adjusting the opening of the
water control valve 82. - (3) As to “Gou”
- The above described “gou” (Japanese) represents the water heating capacity of the
water heater 6. As to “gou”, 1 (gou) is the capacity that the temperature of 1 (L) of water W is raised by 25 (° C.) a minute. The capacity an hour is -
- That is, the formula (1) represents that the combustion and the flow rate are increased and decreased in proportion to “gou”.
- (4) Conversion of “Gou” to US Formula
- Since
- 1 (kcal/h)=3.968 (BTU/h),
- 1,500 (kcal/h)=5,952 (BTU/h)=1 (gou).
- (5) Relationship among Exhaust Temperature, “Gou”, Supplied Water Temperature, Outgoing Hot Water Temperature and Flow Rate
- With reference to the formula (1), “gou” is determined by the deference between a supplied water temperature and an outgoing hot water temperature, and the flow rate. Assuming that a supplied water temperature and outgoing hot water temperature are constant, the temperature of the combustion exhaust E depends on “gou”. Therefore, it is found that in order to lower the temperature of the combustion exhaust E, “gou” may be decreased.
- The above described
water heater 6 controls the combustion of theburner 36 so that an outgoing hot water temperature becomes setting temperatures. If the flow rate changes, the combustion of theburner 36 is controlled according to the change to control the hot water supply temperature within setting temperatures. If the maximum regulated flow rate is gradually reduced by the opening of thewater control valve 82, “gou” decreases along therewith. That is, the decrease of “gou” is narrowing the opening of theproportional valve 48, and thereby, the maximum combustion capacity is regulated. In the other words, if the opening of theproportional valve 48 is gradually narrowed, the opening of thewater control valve 82 is gradually narrowed along therewith, the flow rate of supplied hot water is reduced, and the temperature of outgoing hot water is kept constant. - In such control, to keep an outgoing hot water temperature constant is a priority. However, an outgoing hot water temperature may be changed by adjusting setting temperatures. If an outgoing hot water temperature is changed to keep the flow rate constant, the above described “gou” results in changing.
- This exhaust temperature control will be described with reference to
FIG. 9 .FIG. 9 depicts an example of processing procedure of exhaust temperature control. - This processing procedure is an example of a method for the combustion control or a combustion control program of the present invention. The processing procedure includes the above described temperature control of the combustion exhaust E. In the processing procedure, the upper temperature limit 69 (° C.) and the lower temperature limit 55 (° C.) are set in order to realize the control according to the temperature detected by the
exhaust temperature sensor 108. Between these upper temperature limit (set in 69 (° C.) as a first temperature in the procedure) and the lower temperature limit (set in 55 (° C.) as a fifth temperature in the procedure), a second temperature 66 (° C.), a third temperature 63 (° C.) and a fourth temperature 60 (° C.) are set. - As depicted in
FIG. 9 , the processing procedure starts from the power turned ON. Clearing subtract values for the regulated flow rate is executed as an initial reset (step S101). In this clearing of subtract values for the regulated flow rate, a reset of data representing “gou” regulation before the drivingswitch 121 turned ON (the maximum regulated flow rate and the maximum combustion capacity regulation value) is executed, and the maximum “gou” of an initial setting is set again. - After the power ON, the operation of the driving
switch 121 is monitored (step S102). If the drivingswitch 121 is not turned ON (NO of step S102), the procedure returns to step S101 to be standby. - If the driving
switch 121 is turned ON (YES of step S102), the flow rate of supplied water is monitored (step S103). If the flow rate detected by theflow rate sensor 79 is below a predetermined flow rate (NO of step S103), the procedure becomes standby. - If the flow rate detected by the
flow rate sensor 79 is equal to or over the predetermined flow rate (ON) (YES of step S103), thecombustion fan 42 and theexhaust dilution fan 100 are operated since a demand for hot water is generated by the opening of the hotwater supply faucet 95. The combustion of the fuel gas G is started by theburner 36 and the combustion is maintained (step S104). - During the combustion of the fuel gas G, the temperature of the combustion exhaust E is detected by the
exhaust temperature sensor 108 and the switching operation of the exhaust Hi limit (HHL) 106 is monitored (step S105). The temperature detected by theexhaust temperature sensor 108 and closing information or opening information of theexhaust Hi limit 106 are taken into thecontrol unit 120. - [Control by Opening or Closing of Exhaust Hi Limit 106]
- When the
exhaust Hi limit 106 is opened (YES of step S105), the combustion of theburner 36 is stopped and “gou” is decreased, for example, by 5 (gou) to reduce the regulated flow rate (step S106). The opening or closing of theexhaust Hi limit 106 is continuously monitored, (step S107). If theexhaust Hi limit 106 is closed (NO of step S107), the procedure returns to step S104. - If the
exhaust Hi limit 106 is opened (YES of step S107), whether to be the flow rate OFF or driving OFF, or not is determined (step S108) since the exhaust temperature is over the upper temperature limit H=69 (° C.). The flow rate OFF is the flow rate possible to be regarded as OFF by reducing the flow rate of supplied water. The driving OFF is a state where the drivingswitch 121 is switched OFF. - If the flow rate or driving is OFF (YES of step S108), the procedure returns to step S101. If the flow rate or driving is not OFF (NO of step S108), the procedure returns to step S107.
- In the above processes of steps S105 to S108, if the
exhaust dilution unit 32 is cooled down and theexhaust Hi limit 106 is closed after the combustion is stopped, the combustion is restarted. However, though the combustion is restarted, the combustion is stopped again if the temperature of the combustion exhaust E is higher. Thus, subtraction of the regulated flow rate is executed that the combustion is reduced by 5 (gou) from “gou” when the combustion is stopped to make the exhaust temperature equate to or lower below the predetermined temperature. In this case, driving can be restarted by once closing and then reopening the hotwater supply faucet 95, or by once turning the drivingswitch 121 OFF and then ON again. At that time, the subtract value of the regulated flow rate is cleared. If such processes are repeated, thecontrol unit 120 determines that there is some anomaly, and an alarm may be given from the informingmeans 65. - [Control by Temperature Detected by Exhaust Temperature Sensor 108]
- If the
exhaust Hi limit 106 is closed (NO of step S105), the temperature detected by the exhaust temperature sensor 108 (HTH) is monitored and control according to the detected temperature is executed (steps S109 to S124). - If the temperature detected by the
exhaust temperature sensor 108 is equal to or over the upper temperature limit H=69 (° C.) (YES of step S109), monitoring for a predetermined time since the detection is executed (step S110). If the predetermined time, for example, 1 (sec) has passed since the detection of the temperature equal to or over the upper temperature limit H=69 (° C.) (YES of step S110), stopping the combustion, reducing “gou” by 5 (gou) and reducing the regulated flow rate are executed (step S111), and it is determined whether the temperature of the combustion exhaust E is equal to or below the lower temperature limit L or not (step S112). If 1 (sec) has not passed (NO of step S110), the procedure returns to step S102. - If the temperature is equal to or below the lower temperature limit L=55 (° C.) (YES of step S112), the procedure returns to step S104. If the temperature is over the lower temperature limit L=55 (° C.) (NO of step S112), whether to be the flow rate or driving OFF, or not is determined (step S113). If the flow rate or driving is OFF (YES of step S113), the procedure returns to step S101. If the flow rate or driving is not OFF (NO of step S113), the procedure returns to step S112.
- If the temperature detected by the
exhaust temperature sensor 108 is below the upper temperature limit H=69 (° C.) (NO of step S109), it is determined whether or not the detected temperature is equal to or over the second temperature, for example, 66 (° C.) (step S114). Whether or not a predetermined time, for example, 5 (sec) have passed since the detection of the second temperature is determined (step S115). If 5 (sec) have passed (YES of step S115), the procedure moves to step S111. If 5 (sec) of the predetermined time have not passed (NO of step S115), the procedure returns to step S102. - Like the above, in the processes of steps S109 to S115, detection time and the subtract value of the regulated flow rate vary according to the detected temperature of the combustion exhaust E. For example, if the detected temperature of the combustion exhaust E is equal to or over 69 (° C.), whether detection time, for example, 1 (sec) has passed or not is determined. If at least 1 (sec) or over has passed in a state that the temperature is equal to or over 69 (° C.), the combustion is stopped (step S111). When the combustion is stopped, subtraction of the regulated flow rate is executed and the exhaust temperature is controlled. After that, if the
exhaust temperature sensor 108 detects the temperature 55 (° C.) or below, the combustion is restarted. If the temperature detected by theexhaust temperature sensor 108 is not 55 (° C.) or below, the subtract value of the regulated flow rate is cleared (step S101) by once closing, and then reopening the hotwater supply faucet 95 to enable the combustion to be restarted. - If the detected temperature of the combustion exhaust E is below 69 (° C.), whether to be equal to or over 66 (° C.), or not is determined. If the exhaust temperature is equal to or over 66 (° C.), whether detection time, for example 5 (sec) have passed or not is determined. If the exhaust temperature=66 (° C.) has been maintained for 5 (sec), the combustion is stopped. When the combustion is stopped, subtraction of the regulated flow rate is executed and the exhaust temperature is limited. After that, if the
exhaust temperature sensor 108 detects 55 (° C.) or below, the combustion is restarted. If the hotwater supply faucet 95 is closed and then, reopened before the temperature detected by theexhaust temperature sensor 108 is equal to or below 55 (° C.), the subtract value of the regulated flow rate is cleared (step S101) to enable the combustion to be restarted. - If the temperature detected by the
exhaust temperature sensor 108 is below the second temperature=66 (° C.) (NO of step S114), it is determined whether the detected temperature is equal to or over the third temperature, for example, 63 (° C.), or not (step S116). It is determined whether or not a predetermined time, for example, 20 (sec) have passed since the detection of the third temperature (step S117). If (sec) have passed (YES of step S117), reducing “gou” by 3 (gou) and reducing the regulated flow rate are executed (step S118), and the procedure returns to step S102. - Like the above, in steps S116 to S118, if the exhaust temperature is below 66 (° C.), whether to be equal to or over a predetermined temperature, for example, 63 (° C.), or not is determined. If the exhaust temperature is equal to or over 63 (° C.), it is determined whether detection time, for example, (sec) have passed or not. If the exhaust temperature 63 (° C.) or over have been maintained for 20 (sec), subtraction of the regulated flow rate (3 “gou”) is executed and the exhaust temperature is limited. Differentiating and setting monitoring time longer than step S115 are because accurate temperature information is needed to be taken in since there requires a predetermined time till the flow rate regulation due to continuous temperature detection and since the result of the regulation is not reflected in the exhaust temperature unless a predetermined time has passed from the flow rate regulation.
- If the temperature detected by the
exhaust temperature sensor 108 is below the third temperature=63 (° C.) (NO of step S116), it is determined whether the detected temperature is equal to or over the fourth temperature, for example, 60 (° C.), or not (step S119). It is determined whether or not a predetermined time, for example, 90 (sec) have passed since the detection of the fourth temperature (step S120). If 90 (sec) have passed (YES of step S120), reducing “gou” by 1 (gou) and reducing the regulated flow rate are executed (step S121), and the procedure returns to step S102. - Like the above, in the processes of steps S119 to S121, if the exhaust temperature is below 63 (° C.), whether to be equal to or over a predetermined temperature, for example, 60 (° C.), or not is determined. If the exhaust temperature is equal to or over 60 (° C.), it is determined whether detection time, for example, 90 (sec) have passed or not. If the exhaust temperature 60 (° C.) or over has been maintained for 90 (sec), subtraction of the regulated flow rate (1 “gou”) is executed and the exhaust temperature is limited. Setting monitoring time longer than step S117 as well is because accurate temperature information is needed to be taken in since there requires a predetermined time till the flow rate regulation due to continuous temperature detection and since the result of the regulation is reflected in the exhaust temperature unless a predetermined time has passed from the flow rate regulation.
- If the temperature detected by the
exhaust temperature sensor 108 is below the fourth temperature=60 (° C.) (NO of step S119), it is determined whether the detected temperature is equal to or below the lower temperature limit L=55 (° C.), or not (step S122). If the detected temperature is equal to or below the lower temperature limit L=55 (° C.) (YES of step S122), it is determined whether a predetermined time, for example, 100 (sec) have passed since the detection of the lower temperature limit L=55 (° C.) (step S123). If 100 (sec) have passed (YES of step S123), increasing “gou” by 1 (gou) and increasing the regulated flow rate are executed (step S124) and the procedure returns to step S102. If the detected temperature is equal to or over the lower temperature limit L=55 (° C.) (NO of step S122), the procedure returns to step S102 unless 100 (sec) have not passed since the detection of the lower temperature limit L=55 (° C.) (NO of step S123). - Like the above, in the processes of steps S122 to S124, if the exhaust temperature is below 60 (° C.), whether to be equal to or below a predetermined temperature, for example, 55 (° C.), or not is determined. If the exhaust temperature is equal to or below 55 (° C.), it is determined whether detection time, for example, 100 (sec) have passed or not. If the exhaust temperature 55 (° C.) or below has been maintained for 100 (sec), the regulated flow rate is increased by 1 “gou” to release the regulation of the exhaust temperature. Although the regulated flow rate is increased, the procedure returns to step S102 again to confirm the change of the temperature of the combustion exhaust E after the control to detect the temperature. Increasing the regulated flow rate increases the hot water outgoing capacity again. For example, when the regulated flow rate increases more than need or when outgoing hot water is reduced or a setting temperature is lowered during use, the hot water outgoing capacity can be increased.
- As to the regulated flow rate, in the
water heater 6 of the maximum combustion capacity, for example, 31 (gou) (=Iput: 199,000 (BTU/h)), “gou” for the regulated flow rate=the maximum “gou” of thewater heater 6 in the start of driving. Being raised by 25 (° C.) needs the regulated flow rate 31 (L/min). If 5 (gou) is subtracted from “gou” of the regulated flow rate, “gou” becomes 26 (gou), and the regulated flow rate being raised by 25 (° C.) is 26 (L/min). If the regulated flow rate is set in 31 (L/min), the opening of thewater control valve 82 is narrowed and the regulated flow rate is reduced by 5 (gou) if the temperature of the combustion exhaust E exceeds 69 (° C.). If the regulated flow rate is reduced from 31 (L) to 26 (L), theproportional valve 48 is narrowed maintaining the outgoing hot water temperature, and the combustion capacity is suppressed, the temperature of the combustion exhaust E can be moved to be equal to or below 69 (° C.). In this case, the opening of theproportional valve 48 may be narrowed to reduce the maximum combustion capacity of theburner 36 directly. If the outgoing hot water temperature is tried to be maintained, the flow rate of supplied hot water results in decreasing. - Like the above, the temperature of the combustion exhaust E is controlled between the upper temperature limit H=69 (° C.) and the lower temperature limit L=55 (° C.) by the control of the regulated flow rate. In the other words, the temperature of the combustion exhaust E can be regulated equal to or below 69 (° C.). Moreover, this control of the exhaust temperature is realized by the combustion control maintaining the combustion of a burner.
- Since the temperature of the combustion exhaust E flowing from the
exhaust dilution unit 32 to theexhaust tube 34 can be regulated equal to or below 69 (° C.), a material of low heat-resistance can be used for an exhaust system such as theexhaust path 10. Therefore, a part or all of the exhaust system such as theexhaust path 10 can be composed of a material of low heat-resistance, for example, synthetic resin. - Following effects can be obtained from the embodiment.
- (1) The air supply A2 is mixed with the combustion exhaust E, whose temperature is lowered by secondary heat exchange, using the
exhaust dilution fan 100, and the temperature of the combustion exhaust E flowing into theexhaust tube 34 is lowered so that a material of low heat-resistance such as a resin duct can stand heat. - (2) The temperature of the combustion exhaust E is continuously monitored by installing the
exhaust temperature sensor 108, and the combustion control in response to the exhaust temperature is realized to improve the safety. - (3) If the temperature of the combustion exhaust E is equal to or over the upper temperature limit H, the combustion can be stopped by the installation of the
exhaust Hi limit 106 to provide thewater heater 6 of high safety. - (4) The air supply A2 is mixed with the combustion exhaust E after heat exchange, and the air supply A2 is prevented from flowing into the
secondary heat exchanger 40 at the downstream side. Thus, the exhaust temperature of the combustion exhaust E can be efficiently lowered without reducing the heat exchange efficiency of thesecondary heat exchanger 40. - (5) If the contrary wind CW acts on the
backflow preventer 102 to obstruct thewater heater 6, theexhaust dilution fan 100 is stopped and the combustion continuation is canceled. Thus, thewater heater 6 of high safety can be realized. - In the second embodiment, the control of the exhaust temperature is disclosed that the combustion is reduced to lower the temperature of the combustion exhaust E. This third embodiment discloses that the temperature of the combustion exhaust E is lowered by dilution air from the
exhaust dilution fan 100. - The third embodiment will be described with reference to
FIG. 10 .FIG. 10 depicts an example of processing procedure of an exhaust temperature control process according to the third embodiment. - The processing procedure is an example of the present invention, and includes a process that the rotation speed of the
exhaust dilution fan 100 is increased maintaining the volume of the combustion, and dilution air is increased to lower the exhaust temperature. The processing procedure is executed in the above describedwater heater 6. In the processing procedure, as depicted inFIG. 10 , it is determined whether the detected temperature of the combustion exhaust E is equal to or over 69 (° C.). If the temperature is below 69 (° C.), this process is not executed. - If the detected temperature of the combustion exhaust E is equal to or over 69 (° C.) (step S201), whether “gou” is equal to or over 20 (gou), or not is determined (step S202). If “gou” is equal to or over 20 (gou) (YES of step S202), reduction of “gou” is executed (step S203) as well as the second embodiment, and the procedure returns to the process like the second embodiment.
- If “gou” is below 20 (gou) (NO of step S202), the rotation speed of the
exhaust dilution fan 100 is increased (step S204), and the procedure returns to the process like the second embodiment. - If the combustion is reduced, the temperature of the combustion exhaust E can be lowered. However, in this case, it is predictable that the flow rate desired by a user cannot be obtained. In order to lower the exhaust temperature maintaining the flow rate, the rotation speed of the
exhaust dilution fan 100 maybe increased. By increasing the rotation speed of theexhaust dilution fan 100 and increasing the air supply A2 to be mixed with the combustion exhaust E, the temperature of the combustion exhaust E can be lowered with the air supply A2. - If “gou” is high, for example, over 20 (gou), the combustion exhaust E (the volume of exhaust) results in increasing. The volume of the combustion exhaust E is high so that it is predictable that the temperature of the combustion exhaust E cannot be lowered below the upper temperature limit H=69 (° C.) even if the rotation speed of the
exhaust dilution fan 100 is increased. Thus, a reference value is set for “gou”. In this embodiment, 20 (gou) is set for a threshold level, and “gou” is over 20 (gou), reduction of “gou” is executed. If “gou” is below 20 (gou), the volume of dilution air is increased. - According to such structure, the exhaust temperature of the combustion exhaust E can be lowered by increasing the rotation speed of the
exhaust dilution fan 100. - If “gou” exceeds a predetermined value, reduction of “gou” is executed, and the control of the
exhaust dilution fan 100 is not executed only when “gou” is below predetermined “gou”. Thereby, there is no need to widen capability of theexhaust dilution fan 100, and thecompact water heater 6 is achieved. - Therefore, according to the control of the above processing procedure, the flow rate may be decreased when the used hot water supply capability is high, and the rotation speed of the
exhaust dilution fan 100 may be increased when the capability is low. Thus, the control according to the hot water supply capacity of thewater heater 6 can be realized, and the convenience can be improved. - (1) As to exhaust temperature control, if the exhaust temperature rises by afterheating etc. while the combustion is stopped, the
combustion fan 42 and theexhaust dilution fan 100 may be rotated in the minimum rotation speed when the exhaust temperature is high while the combustion is stopped or during the detection of theexhaust Hi limit 106. - By the detected temperatures of the hot
water temperature sensor 88 at the outlet of theheat exchanger 38, the temperature detected by theexhaust temperature sensor 108 and a switching output of theexhaust Hi limit 106, the operation of thecombustion fan 42 and theexhaust dilution fan 100 may be determined as depicted inFIGS. 11 and 12 . According to the control using the detected temperatures of the hotwater temperature sensor 88 at the outlet of theheat exchanger 38, the temperature detected by theexhaust temperature sensor 108 and a switching output of the exhaust Hi limit 106 like the above, freezing can be prevented. - (2) The
backflow preventer 102 has the structure that opening and closing positions are automatically determined according to wind pressure in the above embodiments. The contrary wind CW acting on thebackflow preventer 102 may be detected, and the opening and closing of thebackflow preventer 102 may be controlled electrically by detected wind pressure and the wind pressure from the air supply A2. - (3) While the
exhaust dilution duct 96 is set short and theexhaust dilution fan 100 is placed in the vicinity of theexhaust dilution unit 32 in the above embodiments, the inventions are not limited thereto. As depicted inFIG. 13 , theexhaust dilution duct 96 may be arranged in parallel to thecombustion chamber 28, and the height of theexhaust dilution fan 100 may be brought to the same as thecombustion fan 42. - (4) The fuel gas G is exemplified as fuel in the above embodiments. Fuel is not limited to gas, and may be liquid.
- (5) The place for introducing (mixing) dilution air by the dilution fan is made to join the exhaust outlet of the combustion air at the downstream side of the heat exchangers, for diluting the combustion air. A backflow preventer may be built in so as to be used for extended exhaust pipe.
- (6) An exhaust temperature sensor monitoring an exhaust temperature may be placed at the exhaust outlet, and dilution fan rotating control means or combustion control means may be provided.
- (7) A dilution fan and a dilution path from the dilution fan to the exhaust outlet may be placed at a proper place in the housing, and the mixture part with the combustion exhaust may be provided so as not to prevent combustion exhaust.
- (8) In the above embodiments, the
exhaust Hi limit 106 is used for the detection of the exhaustion temperature. The inventions are not limited thereto. Operation characteristics of theexhaust Hi limit 106 may be realized by a plurality of the exhaust temperature sensors that when the temperature of the combustion exhaust E reaches the upper temperature limit, conduction is switched to non-conduction when the temperature of the combustion exhaust E drops to the lower temperature limit, non-conduction is switched to conduction. - While the most preferred embodiments of the combustion apparatus, the method for combustion control, the combustion control board, the combustion control system and the water heater have been described hereinabove, the present invention is not limited to the above description, and it is a matter of course that various variations and modifications can be made by those skilled in the art within the scope of the claims without departing from the spirit of the invention disclosed herein, and needless to say, such variations and modifications are also encompassed in the scope of the present invention.
Claims (17)
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